Static values are automatically compensated and capacitance variations are converted to frequency changes.
Further detection is based on special algorithm that use time division and multiple frequency. There is also
built in automatic compensation, that eliminate temperature and humidity changes. To work properly in RF noise,
sensors have advanced digital filtering stage. This ensures reliable function.

When finger is out of touch pad, input capacitance is lower than if finger is near touch pad. This is monitored by
touch sensor and as soon as capacitance change with time match pattern that define „touch”, sensor output is activated.

Sensitivity is adjustable parameter. Simple devices have special control pin, that can be used to set input sensitivity
to low, middle or high level. I2C controlled devices has special registers, where can be set sensitivity as well as
other parameters.

Some sensors can even detect touch intensity. For example TSM12 can detect intensity in three steps. Application then
may respond by small (f.e. volume) change to soft touch and by high volume change to hard touch.

Relative permittivity of some substances

Substance

εr

Vacuum

1

Air

1,000 59

Expanded polystyrene

1,03

Wood

2,04 - 7,3

Amber

2,6 - 2,8

Plexiglass

3,4

Glass

3,8 - 19

FR-4

4,5

Ice

4,8

Porcelain

5,5 - 6,5

NaCl (monocrystalline)

5,9

Marble

7 - 8

Silicon

11,7

Germanium

16 - 16,4

Water

81

For more application circuits and component explanation see detail documentation available on our web.